(a) Field of the Invention
The present invention relates to a welding device for a stretch bender. More particularly, the present invention relates to a welding device for a stretch bender that welds flange portions of a shaped beam before extracting the shaped beam on which stretch bend forming is completely performed such that the flange portions are prevented from being overlapped with each other when extracting the shaped beam.
(b) Description of the Related Art
Generally, a bending machine forms a beam to have a curvature. Particularly, the bending machine is adapted to bend a straight shaped beam to have a predetermined curvature formed by roll forming so as to manufacture a bumper beam for vehicles.
The bending machine bends a straight beam 1 illustrated in FIG. 1 so as to manufacture a curved shaped beam 3 having a predetermined curvature illustrated in FIG. 2.
Herein, the straight beam 1 includes a front surface F1, an upper surface F2 and a lower surface F3, and a groove portion G is formed at a center portion of the front surface F1. In addition, flange portions 5 are positioned respectively at an upper portion and a lower portion of the groove portion G. The straight beam 1 illustrated in FIG. 1 has a width W relatively wider than that of a bumper beam used in a car, and can be used as the bumper beam of a large truck.
However, if a high strength straight beam 1 having relatively wider widths of the upper surface F2 and the lower surface F3 is bent using a typical roll bender or a typical round bender, formability may be deteriorated due to high strength of the straight beam 1.
In addition, if the straight beam 1 is made of high strength material, precise curvature cannot be formed due to spring back, and dimension error and bad assembly may occur.
To solve such drawbacks, a stretch bender is used. The stretch bender pulls both ends of the high strength shaped beam having relatively wider width to the both sides and performs stretch bend forming on the shaped beam against a bending die having a predetermined shape. Therefore, strength and spring back of the shaped beam can be controlled and dimensional accuracy of the curvature may be enhanced.
Referring to FIG. 3, the stretch bender 10 includes a bender base 20, a bending die 30, a rotating unit 40 and a stretching unit 50.
A hinge frame 21 is mounted at a rear portion of a middle portion of the bender base 20.
The bending die 30 is mounted at a center portion of an upper surface of the bender base 20 so as to bend the straight beam 1 to have the predetermined curvature.
A curvature forming groove 33 having the predetermined curvature is formed at a front surface of the bending die 30.
In addition, a pair of rotating units 40 is mounted at both sides of the upper surface of the bender base 20. A pair of rotating shafts 41 is mounted at the bender base 20 corresponding to both side portions of the bending die 30, and a rotating table 43 of each rotating unit 40 is adapted to be rotated about the rotating shaft 41 by operation of a cylinder.
The rotating table 43 receives rotating torque from a rotating cylinder 45, and the rotating cylinder 45 is mounted between the hinge frame 21 and the rotating table 43.
In addition, the stretching unit 50 is mounted on the rotating table 43 of each rotating unit 40. The stretching unit 50 clamps both end portions of the shaped beam 1 and pulls the both end portions of the shaped beam 1 with a predetermined pressure so as to perform stretching operation.
That is, stretching unit 50 includes a stretching cylinder 51 mounted on one side portion of the rotating table 43 and a toggle clamper 54 provided at a front end of an operating rod of the stretching cylinder 51. The toggle clamper 54 is slidably mounted along a guide rail 55 mounted on the rotating table 43.
Herein, the toggle clamper 54 includes a clamping cylinder unit 56 and a clamping member 57. The clamping cylinder unit 56 operates the clamping member 57 such that the clamping member 57 clamp an end portion of the shaped beam 1 so as to maintain stretching operation by the stretching cylinder 51.
Therefore, if the straight beam 1 is supplied in front of the bending die 30, the stretching cylinder 51 moves forward and the toggle clampers 54 clamp both end portions of the straight beam 1.
At this state, if the rotating cylinder 45 moves rearward so as to pull an end portion of the rotating table 43 rearward, the rotating table 43 rotates about the rotating shaft 41. At the same time, the stretching cylinder 51 moves rearward so as to move the toggle clamper 54 rearward. Therefore, the toggle clampers 54 pulls the both end portions of the straight beam 1 so as to stretch the straight beam 1.
Therefore, the straight beam 1 is stretched and bent by the bending die 30 such that the shaped beam 3 having the predetermined curvature is formed.
According to a conventional stretch bender, however, the straight beam 1 is fitted in the curvature forming groove 33 of the bending die 30 after the straight beam 1 is formed to be the shaped beam 3 having the predetermined curvature along the curvature forming groove 33 of the bending die 30. It is difficult for a worker to extract the shaped beam 3 for himself, and the flange portions 5 positioned in the groove portion G may be overlapped with each other by force exerted when extracting the shaped beam 3.
If the flange portions 5 of the shaped beam 3 are overlapped with each other, working efficiency and welding quality may be deteriorated and accordingly, marketability may be also deteriorated at spot welding or laser welding that is a next process.
In addition, since additional device or apparatus for disposing the flange portions 5 of the shaped beam 3 at their home positions are necessary so as to prevent such problems, investment cost may be increased and productivity may be deteriorated due to extended manufacturing cycle time.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.